Low levels of lead, previously considered safe, have been found to cause high blood pressure and strokes in adults and to adversely affect the development, mental abilities and hearing of children. Most of the lead in water that is consumed originates from corrosion in water-delivery systems and home plumbing. Drinking water delivered from municipal and other water suppliers is not normally high in lead content. Thus, the primary source of lead is derived from subsequent corrosion of service connections, pipes, fixtures and other plumbing parts of systems which distribute water tom end consumers. Much of this lead-bearing plumbing is privately owned, that is, it is installed permanently within homes and buildings. Because of this, as a practical matter, the reduction of lead in drinking water has been accomplished primarily by introducing corrosion inhibitors into the drinking water, by adjusting the alkalinity level of the water by raising its pH value to eight, by service connection replacements of water distribution systems to homes or buildings, and by public education concerning the danger of lead in drinking water. Substantial levels of lead have also been found in water delivered to drinking fountains such as those installed in office buildings, schools and other public facilities.
The replacement of plumbing in a home or other building is seldom a practical solution to achieve the desired reduction of lead and other heavy metals in drinking water at point-of-use.
Purification of water at point-of-use is a more logical solution to the problem. Conventional technologies which can be used for this purpose include reverse osmosis, distillation, and filtration utilizing activated carbon and ion-exchange resins. Reverse osmosis and activated carbon filtration units have been widely employed for home drinking water treatment to remove a variety of contaminants, primarily organics from drinking water. These filtration units can also remove lead. Further, distillation and ion-exchange resin units are also effective in removing lead from drinking water. These technologies, however, are non-specific in that they are not directed primarily to the removal of lead and other heavy metals, and for this reason their lead-removal capacities for drinking water are significantly less than might otherwise be the case. The situation is aggravated if alkalinity of the water is increased or corrosion inhibitors are added, which are frequent methods utilized by water treatment plants to reduce the corrosivity of their treated water. Current systems of reverse osmosis do not work well using line pressures which exist in most homes. In addition, their capacities to produce purified water are relatively low. A high pressure pump needs to be added which may prove expensive and impractical. Single-stage distillation units are quite energy intensive and, for this reason, generally should be avoided. Thus, most known technologies for reducing lead and other heavy metals in drinking water at point-of-use are either capital intensive or costly to operate, or both.
The use of alumina for water filters is known. In addition, gamma alumina is known to be selective for heavy metals. Unfortunately, the prior art experience with alumina has not demonstrated that this filtration substance to be a satisfactory solution for point-of-use filtration of drinking water at most locations from the standpoints of efficiency and capacity.
It is often desirable to remove chlorines and chloramines from the water in addition to heavy metals. A method for treating water to remove undesirable constituents contained therein, such as chlorine and nitrate constitutes, is disclosed in U.S. Pat. No. 4,642,192, to D. Heskett, of Feb. 10, 1987. This discloses a method which utilizes a filter consisting of metal particles of a metal alloy composed of copper and zinc, or, in other words, a brass alloy. But the brass alloy leaches copper and zinc into the water that has passed through it. Moreover, brass alloys frequently contain lead, which will also leach from such filters. With a filter of the type taught by the foregoing Patent to Heskett, the water filtered therethrough had 1.2 ppm of copper and 3.6 ppm of zinc. The latter may be in the form of zinc chlorides which contaminate not only of the water, per se, but also may be suspended in vapor and the surrounding air when one takes a shower with water that has been so filtered. Without a filter of this type, chlorine is likely to be present in the household water, which can adversely affect beverages and food that utilize the water for their preparations. Moreover, it has been found that chlorine ingestion, at least in animal studies, alters the body's handling of cholesterol and fats. Accordingly, there is a need not only to reduce or eliminate the chlorine in drinking water or water received at point-of-use, but also wherein filters are provided to eliminate or substantially reduce the chlorine content in water further to eliminate or substantially reduce metals such as zinc and copper, in addition to lead, which may be leached therefrom.
The following is a list of literature and other publications which reflect the skill of the art and, for such purposes, are incorporated herein by reference:
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